NEUTRAL PHOSPHATE ADMINISTRATION GENERATES AND MAINTAINS RENAL METABOLIC ALKALOSIS AND HYPERPARATHYROIDISM

We examined the effects of chronic intravenous neutral phosphate admin istration on systemic acid-base equilibrium and parathyroid function i n six normal, NaCl-replete male human subjects under metabolic balance conditions. The subjects received 4.35 mmol of neutral sodium phospha te . kg body wt(-1) . day(-1) intravenously and continuously for 7 day s and the same amount of sodium as NaCl during control and recovery. B lood pH increased from 7.388 to 7.411 (P < 0.001) and plasma bicarbona te from 23.5 to 26.0 mmol/l (P < 0.001). Urinary pH increased from 6.5 8 to 6.79 (P < 0.001). Net acid excretion increased from 59 to 100 mmo l/24 h (P < 0.001). Plasma ionized calcium concentration decreased and plasma phosphate concentration increased transiently. Serum intact pa rathyroid hormone increased from 24 to 62 pg/ml (P < 0.001). Chronic p hosphate administration also resulted in a significant increase in ren al phosphate clearance (35 to 229 ml/min) and decrease in the fraction al excretion of calcium (1.8 to 0.9%). Thus chronic intravenous phosph ate administration generates and maintains renal metabolic alkalosis i n salt-replete humans and induces hyperparathyroidism. The severity of metabolic alkalosis is mitigated by an apparent increase in effective endogenous acid production as evidenced by the significant increase i n steady-state net acid excretion.